1. Field of the Invention
The present invention relates to a base station of a CDMA mobile communication system and an operation method thereof, and in particular to a base station for compensating a route delay fixed between a base station and a mobile station of a CDMA mobile communication system and an operation method thereof which are capable of effectively compensating a route delay in a relay unit or satellite on a communication route between a base station and a mobile station due to a hardware-based delay of a modem ASIC of a channel card of a CDMA base station.
2. Description of the Background Art
In a conventional CDMA mobile communication system, all mobile stations and base stations operate based on a time synchronization to a reference clock signal of a CDMA system. In addition, the mobile station is set synchronously with the base station by obtaining a time information based on a message transmitted from the base station and setting a reference time. At this time, the reference time set by the mobile station is delayed compared to the referee time of the base station due to a delay of a propagation signal from the base station to the mobile station and a signal processing delay by the mobile station.
In addition, the mobile station transmits a signal in synchronization with the reference time. The reverse direction link signal is transmitted based on a synchronization, however, this signal is received with a time delay (hereinafter called bidirectional propagation delay) at a system reference clock.
In addition, at the CDMA system, the maximum limit value of the bidirectional propagation delay is limited based on a hardware construction by a base station modem ASIC(Application Specific IC), and the maximum limit value is about 416 μs. When computing the maximum limit value based on a cell communication radius by an open area, it corresponds to about 62 Km(416 μs*light speed/2).
However, in the conventional CDMA system, the maximum cell communication range is limited based on a timing by the base station modem ASIC. In addition, when using a satellite or a relay unit between the base station and the mobile station, a fixed route delay additionally occurs, so that the cell communication radius is decreased by the above-described additional route delay amount.
As another problem, when the above-described additional route delay exceeds a the maximum bidirectional propagation delay time between the base station and the mobile station, a communication failure occurs.